"Where are They?" -Fermi Paradox Answered
Using a computer simulation of our own galaxy, the Milky Way, Rasmus Bjork, a physicist at the Niels Bohr Institute in Copenhagen, proposed an answer to the famous Fermi Paradox about the existence of . Bjork proposed that an alien civilisation might build intergalactic probes and launch them on missions to search for life.
He found, however, that even if the alien ships could hurtle through space at a tenth of the speed of light, or 30,000km a second, - Nasa's current Cassini mission to Saturn is gliding along at 32km a second - it would take 10 billon years, roughly half the age of the universe, to explore a mere four percent of the galaxy.
Like humans, alien civilisations could shorten the time to find extra-terrestrials by picking up television and radio broadcasts that might leak from colonised planets. "Even then," he reported in the New Scientist, "unless they can develop an exotic form of transport that gets them across the galaxy in two weeks it's still going to take millions of years to find us. There are so many stars in the galaxy that probably life could exist elsewhere, but will we ever get in contact with them? Not in our lifetime."
Others in the scientific community, such as George Dvorsky believe that what Bjork should have consisdered is the possibility that advanced civilizations might proliferate von Neumann self-replicating probes using molecular assembling nanotecynology. Initially, the spread of von Neumann probes would be slow, but like any exponential process, progress would eventually explode, with the possibility that these probes could reach all four corners of the Milky Way galaxy anywhere from 5 to 50 million years.
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